There are some process of manufacturing of Compound Fertilizer. We can get two different sizes fertilizer from these process.
Normal/Regular Size:
i)
Steam or water granulation
Granular
Size:
ii)
Chemical granulation
iii)
Drop formation (Prilling)
v)
Dry mixing/Blending
iv) Compaction granulation
i) Steam/Water granulation:
In
the steam/water granulation process, compound fertilizers are formed by
agglomeration. The solid raw materials are proportioned and usually premixed
before being fed to the granulator where granulator where agglomeration is
initiated. In the granulator (usually a rotary drum) steam and/or water is
added to provide sufficient liquid phase and plasticity to cause the dry raw
materials to agglomerate into product size. The moist and plastic granules are
dried usually in a rotary drum type, fuel fired dryer and screened to remove
the product size fraction. If we add 50% Nitrogen, 40% Phosphorus, then we’ll
add 10% of additive/filler. Mixing of two/three raw materials in a place is
called pre-mix.
Figure: Flow diagram of Steam/Water Granulation
ii) Chemical Granulation:
Chemical granulation is the most complex method for
preparing compound fertilizers. The chemical granulation process is very
similar to the previously described steam/water granulation process except that
most of the liquid phase required to achieve granulation is obtained by various
chemical reactions such as:
i) Ca(H2PO4)2.H2O+(NH4)2SO4+H2O
= CaSO4.2H2O+2NH4H2PO4
ii) (NH4)2SO4+2KCl =
K2SO4+2NH4Cl
iii) NH4NO3+KCl = KNO3+NH4Cl
iv) (NH4)2SO4+CaSO4+H2O
= (NH4)2SO4.CaSO4.H2O
v) K2SO4+CaSO4+H2O
= K2SO4.CaSO4.H2O
vi) H3PO4+(NH4)2HPO4
= 2NH4H2PO4
vii) Ca(H2PO4)2.H2O+4CO(NH2)2
= Ca(H2PO4)2.4CO(NH2)2+H2O
Note:
iv, v & vi no. show additive reactions.
iii) Drop formation (Prilling):
In this process, the fertilizer mixture solution is
concentrated to approximately 96-98% solids before it is introduced to the top
of the prilling tower through prilling bucket. The prilling bucket are designed
to produce droplets of the molten fertilizer mixture that upon solidification,
will yield the desired granule (prill) size.
Figure: Flowchart/flow diagram of drop formation
(prilling)
iv) Compaction granulation:
In
this process, mechanical force is used to form dense particle from finely
divided (non-granular) solid material. With compaction granulation, the dry
materials are first proportioned and mixed to achieve desired nutrient ratio.
The mixture is then fed to a pressure poll compaction machine that forms the
powdered material into a dense hard sheet of about 2-3 cm thick and 60-100 cm
wide. The compacted sheet is then crushed in a controlled manner to form
smaller particles. The crushed material is screened to obtain the desired
product size.
iv) Dry mixing (Blending):
Figure: Flow diagram of manufacturing of
compound fertilizer by fertilizer blending plant